in the morning after my car sits all night when I start it up there is a loud rattling sound coming from the engine compartment as well the engine fan is extremely loud
I have the same car and though I haven't had this problem myself, I think there is a good chance you fan clutch is bad on your main, engine driven mechanical fan.
To see if this is the problem, do this:
- With the car cold and turned off, pop the hood and try to spin the mechanical fan by hand. If you can't, the fan clutch is defintely bad.
- If that is inconclusive, try this *VERY CAREFULLY*: Get a rolled up newspaper, start the car, and insert the newspaper into the fan while it is spinning. if it stops the fan, the clutch is likely OK. if it doesn't, again, the clutch is likely bad.
Some tips non replacing the clutch if it's bad:
1) The fan clutch is held on with a large bolt with REVERSE threads. I don't know the mm siuze, but my very large crescent works fine on it.
2) It may be hard to remove as the clutch may allow it to spin when you put torque on the nut. Many people have success by using a large mallet and striking the wrench twice to dislodge it. Others use either a long screwdriver to wedge between the nuts to hodl it or 2 10mm box end wrenches on 2 of the pulley nuts to keep it still. this is hard to explain but will make sense once you see it.
*** There is also a bmw tool to hold the pulley still, but it is expensive and not common, so i am assuming you don't have one.